Assertion (A): Parallel current in wires attracts to each other due to magnetic force.
Reason (R): Two electron beams moving parallel to each other repels to each other due to electric force.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Wires with parallel currents attract due to magnetic force, so (A) is true. Two parallel electron beams experience electric repulsion due to like charges, so (R) is true. However, the magnetic force (A) and electric force (R) are distinct phenomena. Thus, (R) does not explain (A).
Assertion (A): Force on a current carrying wire of length \(dvec{l}\) placed in magnetic field \(vec{B}\) is given by \(d\vec{F} = Id\vec{l} \times \vec{B}\).
Reason (R): Net force on a current carrying loop in a non-uniform magnetic field must be non-zero.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
The Lorentz force law states \(d\vec{F} = I(d\vec{l} \times \vec{B})\), so (A) is true. For a loop in a uniform field, net force is zero; in a non-uniform field, it is generally non-zero, so (R) is true. However, (R) is a consequence of the force law, not an explanation of the force law itself.
Assertion (A): If a flexible loop (irregular shape) carrying current is located in an external uniform magnetic field then it may be changed to circular shape.
Reason (R): A current carrying loop in uniform magnetic field has zero net force.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true: A current loop in a magnetic field tends to maximize its enclosed area to minimize its magnetic potential energy \(-\vec{M} \cdot \vec{B}\). A circle provides the maximum area for a given perimeter.
Reason (R) is true: The net force on a closed loop in a uniform magnetic field is zero. (R) does not explain (A); the shape change is due to torque and area maximization, not the zero net force. Both are true, but (R) is not the explanation for (A).
Assertion (A): A current-carrying coil placed in a uniform magnetic field experiences a force which depends on the orientation of plane of the coil relative to the field direction.
Reason (R): A current-carrying conductor placed in a magnetic field experiences a force \( F = I L B sin \theta \).
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
A current-carrying coil in a uniform magnetic field experiences a torque \( \tau = NIAB sin \alpha \), where \( \alpha \) is the angle between the area vector and the magnetic field. This torque and the resultant forces clearly depend on the coil's orientation, making (A) true. The force on a segment of a current-carrying conductor is given by \( F = ILB sin \theta \). This fundamental principle explains the origin of the forces acting on the sides of the coil, leading to the overall torque and forces in (A). Both (A) and (R) are true, and (R) is the correct explanation of (A).